This part was taken from a Motronic M1.7 engine control unit (ECU), which was used on the M42 engine of the BMW E30 318iS.

Functionally, this chip serves a variety of purposes, with the best high-level description stating that it is a programmable peripheral interface (PPI). It bears some similarity to standard devices such as the 8155 and 8255, but it is clearly a custom part based on the number of IO's. Some of the functions it provides are:

- Latching of the low-byte address (from the data lines) for external ROM and RAM accesses - Some internal digital logic which takes the A13-15 inputs and outputs enable/disable signals on other IO pins for other ICs - Provides additional latching IO pins - Provides additional IO pins - Provides additional input-only pins - Interfaces with the external L-Line diagnostic interface which is used by various code scanner tools to initiate communication on the faster K-Line interface

Label (top):

SIEMENS
B57828 (Bosch internal PN)
BD26401
AC ©INTEL'80
9025

Decap Steps:
(Bic lighter + water quench) x 4 cycles
Selective crushing with pliers and bench vise

Capture Details:
Imaging device: Keyence VHX-2000
Magnification: 200X

Markings:
SIEMENS
1993
M230-G .67

Note: The die was badly damaged during decapsulation. A future effort at doing this chemically is on the to-do list.